JPH05339401A - Method for forming polybenzimidazole coating film - Google Patents

Abstract

PURPOSE:To form a polybenzimidazole coating film having excellent film strength and adhesivity to a substrate. CONSTITUTION:The objective method for forming a polybenzimidazole coating comprises step of (1) forming a coating film of a PBI solution on a substrate and (2) drying the above coating film by gradually raising the temperature of the coating film from 50-70 deg.C to 150-220 deg.C. This method may further comprise a step of heating the dried film at 300-500 deg.C to crosslink the PBI. A coating film having high strength, heat-resistance, heat-insulation, chemical resistance and abrasion resistance and low frictional coefficient can easily be formed on a substrate by this method to obtain a new material having improved surface properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a film of polybenzimidazole (hereinafter also referred to as "PBI").

[0002]

BACKGROUND OF THE INVENTION PBI is a stable heterocyclic polymer and its method of preparation is described in a number of US patents including US Reissue Pat. No. 26,065 and US Pat. No. 3,313,783.
No. 3,509,108, 3,518,234
No. 3,555,389, 3,433,772
No. 3,408,336, 3,578,644
No. 3,3,549,603, 3,708,439
No. 4,154,919, 4,312,976
No. 4,377,546 and 4,549,388
No. Further, the manufacturing method of PBI is described in J.
P. Critchley, G .; J. Knight and W.W. W. Wright, “Heat-Resistant Polymers—Technically Useful Materials (Heat-Resistant Polym
ers-Technologically Usefu
l Materials) ”Plenum Pres
s, New York (1983), Nos. 259-322.
It is also explained on the page.

PBI has a heat distortion temperature of 435 ° C.,
It has significantly higher heat resistance than polytetrafluoroethylene (hereinafter also referred to as "PTFE") and silicone rubber. The wear coefficient of PBI is 100 hours, PV = 50
It is 29 at 000 and is excellent in wear resistance. Therefore, by applying PBI to the surface of various substances, it becomes possible to provide a material excellent in high heat resistance, high chemical resistance, high abrasion resistance, and the like.

However, the melting point of PBI is 5
Since it is extremely close to 80 ° C., a stable hot melt state cannot be easily obtained. Therefore, it is difficult to apply PBI by a known hot melt method. Further, since PBI has excellent chemical resistance, it was difficult to apply it by the solvent dilution method.

[0005]

In view of the above problems, it is an object of the present invention to provide a method for forming a PBI coating film having excellent film strength and adhesiveness with a substrate.

[0006]

In order to solve the above-mentioned problems, the method of forming a PBI film of the present invention comprises the following steps (1) and (2); (1) a coating film of a PBI solution on a substrate. And (2) the temperature of the coating film from 50 to 70 ° C. to 150 to 2
A step of drying the coating film by gradually raising the temperature to 20 ° C .;

The PBI used in the present invention is preferably poly-2,2 '-(m-
Phenylene) -5,5'-bibenzimidazole; The molecular weight of PBI used in the present invention is not particularly limited, but the number average molecular weight is 2000 to 10
Particularly good results are obtained with a PBI of 0000.

In the present invention, the solvent of the PBI solution used for applying the PBI coating film may be a solvent generally used in producing a dry spinning solution of PBI. Preferably, the solvent is at least one solvent selected from the group consisting of N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide and N-methyl-2-pyrrolidone. The most preferred solvent in the present invention is N, N-dimethylacetamide.

In the present invention, terpenes and / or ketones may be added to the solvent as a mixed solvent. Such terpenes used in the present invention include, for example, kerosene. On the other hand, such ketones used in the present invention include methyl ethyl ketone. In this way, by mixing two or more kinds of solvents having different boiling points and viscosities, the drying efficiency of the PBI coating film and the control of the film thickness are improved without impairing the solubility of the solvent. That is, for example, N, N
-Dimethylacetamide has a boiling point of 167 [deg.] C. and is classified as a high temperature solvent. Therefore, by mixing it with a low boiling point solvent, the drying efficiency is improved and the generation of bubbles due to residual solvent and heating evaporation can be reduced. it can.

In order to dissolve PBI in the solvent in the present invention, for example, an apparatus capable of forced agitation under high temperature and high pressure conditions using an autoclave and / or a homogenized mixer or a sand mill is used.

In the method of the present invention, any known coating method can be used to apply the PBI solution to the substrate. Such methods are, for example, dip coating, electrostatic coating, spray coating, roll coating and the like.

The coating of PBI solution applied to the surface of the substrate is then dried. The solvent used in the present invention is a high-boiling solvent (for example, N, N-dimethylacetamide has a volatilization point of 63 ° C and a boiling point of 167 ° C).
However, normal drying is not suitable. Further, when the temperature of the coating film is rapidly increased, bubbles are likely to be generated inside and on the surface of the coating film due to the residual solvent and the heat evaporation of the solvent, so that a tough coating film cannot be obtained. Then, the inventors of the present invention have conducted intensive studies on the drying conditions of the coating film, and as a result, found that there is a correlation between the temperature rising rate and the generation of bubbles. Further, it has been found that this temperature rising rate depends on the film thickness of the PBI film, and that a better quality PBI film can be obtained under more suitable conditions.

That is, when the coating film of the PBI solution is dried in the present invention, the temperature of the coating film is 50 to 70 ° C. to 15 ° C.
It is necessary to gradually raise the temperature to 0 to 220 ° C. Preferably, the starting temperature is 55-65 ° C and the final temperature is 190-210 ° C. The heating rate depends on the film thickness of the coating film, but is generally 15 ° C./minute or less. Table 1 shows the relationship between the thickness of the coating film and the preferable heating rate.

[0014] As is clear from Table 1, the preferable heating rate decreases as the thickness increases. Film thickness is 1 ~ 5000μ
In the case of m, the rate of temperature rise is preferably 0.5 to 15 ° C./minute. Note that the temperature rise curve does not necessarily have to be linearly upward, and for example, may have a temporarily horizontal state, the slope of temperature rise may change, or the temperature may rise stepwise. It may rise gently along a curve.

In order to obtain a uniform and strong PBI coating film, it is preferable to maintain the viscosity of the solvent at the time of drying the PBI coating film at an appropriate value. Also, without generating bubbles,
It is preferable to volatilize the solvent as quickly as possible.
To this end, the substrate and / or PBI solution are mixed with 50 to 10
It is preferable to preheat to 0 ° C, preferably 60 to 70 ° C.

More preferably, the substrate and the PBI solution are 5
After preheating to 5-65 ° C., the PBI solution is applied to the substrate, then the temperature of the coating is gradually raised to a temperature above the boiling point of the solvent. Final temperature is 1
It is preferably 90 to 210 ° C.

In the present invention, preferably, in addition to the above steps, a post-heating step of further raising the temperature of the PBI coating film may be carried out after the final temperature of the above drying is reached. A thermal condensation and / or cross-linking in the subsequent heating step gives a higher molecular weight PBI coating. The PBI coating thus obtained is tougher,
It is useful in various fields. This post-heating step is performed by heating at 300 to 500 ° C. for a certain period of time. Particularly preferably, it is carried out at 320 to 370 ° C. Also,
The post-heating step may be performed after cooling once after the completion of the PBI coating film drying step.

After being dried at the above-mentioned final temperature or after performing the above-mentioned post-heating step, if it is rapidly cooled, it is contracted due to thermal strain generated during the drying or post-heating or due to the difference in thermal expansion between PBI and the substrate. Occurs, and cracks or cracks are likely to occur on the surface of the PBI coating. In order to prevent this, it is preferable to set a constant cooling rate and gradually cool. The PBI coating film of the present invention thus cooled becomes a tough coating film that does not cause the cracks and cracks described above even if the temperature is rapidly raised / cooled thereafter.

In another aspect of the present invention, the substrate and PBI are
An intermediate layer can be provided between the film and the coating. This is because the provision of the intermediate layer may improve the adhesion between the substrate and the PBI coating. As the intermediate layer, for example, PTFE
Or silicone rubber can be used.

In the present invention, the PBI solution may contain an internal filler, a binder resin substance or the like.
By including an internally added filler in the PBI solution, the self-lubricating property and electric conductivity of PBI can be improved. Such internal fillers are, for example, SiC, various metal powders, carbon such as graphite, and glass. By improving the self-lubricating property, the slipperiness of the coating surface is improved. On the other hand, by improving the electrical conductivity, generation and accumulation of static electricity on the surface of the coating film can be prevented. For example, by internally adding graphite to PBI, the volume resistivity value of PBI can be lowered to 10 ⁶ to ⁸ to 10 ¹⁴ Ωcm.

The surface hardness of PBI is as very high as 110 on the Rockwell hardness K scale, but elasticity and surface hardness can be improved by including a binder resin substance in the PBI solution. By improving elasticity and surface hardness, it becomes possible to give a degree of freedom to the contact area when the coating film surface comes into contact with another material. Such a binder resin material is, for example, HTV (High
Temperature Vulcanized Silicone Rubber, RTV (Room Temperature)
re Vulcanized) Silicone rubber, LTV
(Low Temperature Vulcaniz
ed) A homopolymer of a fluorine-containing monomer such as silicone rubber or PTFE, or a copolymer of a fluorine-containing monomer and another monomer.

In the present invention, the substrate on which the PBI solution is applied is not particularly limited, but aluminum alloys, metals such as steel and stainless steel, ceramics, rubbers and plastics are preferably used. The shape of the substrate is not particularly limited, but examples thereof include a roll shape, a rope shape, a plate shape, a sheet shape, and a spherical shape.

The PBI coating according to the present invention can be applied to various fields. For example, rolls and paper separation nails in toner fixing devices for electrophotographic copying machines and printers,
Alternatively, it is applied to frying pans and the like.

The present invention will be described in more detail with reference to the following examples.

[0025]

Example 1 Poly-2,2 '-(m-phenylene) -5,5'-bibenzimidazole (Cela as PBI)
Zole (registered trademark), manufactured by Hoechst Celanese Co., Ltd. was used. Using a homogenized mixer at room temperature, 1
It was dissolved in N, N-dimethylacetamide under the conditions of 80 rpm and 8 hours to prepare a PBI solution having a concentration of 10% by weight. An aluminum roll having a diameter of 30 mm was used as the substrate. After preheating the PBI solution to 60 ° C., the PBI solution was applied to the surface of an aluminum roll at room temperature (23 ° C.) by a roll coater. Then the starting temperature 60
The coating film was dried at a temperature rising rate from 7 ° C / min to 7 ° C. The final temperature was 200 ° C. As a result, a 20 μm-thick PBI coating film was obtained on the surface of the aluminum roll. The heat transfer coefficient of the PBI coating thus obtained is 0.
It was 41 W / m ° C and the heat distortion temperature was 435 ° C.
Other performances are shown in Table 2.

In Table 2, abrasion resistance indicates the hardness of a pencil when the surface of the coating is scratched by a pencil having a specific hardness and the coating is scratched. Thereby, the film strength and hardness are judged. The dynamic friction coefficient is C1018 steel and the pressure is 7
kg / cm ² , speed 5 m / s, mating material and PB
The surface roughness of the I coating was measured under the condition of 16 rms. Also,
The heat deflection temperature was AS 8.5 at a load of 18.5 kg / cm ^2.
It carried out based on TM D695.

[0027]

Example 2 The same operation as in Example 1 was performed, except that the temperature was further raised after the final drying temperature of 200 ° C. and the PBI was crosslinked at 350 ° C. As a result, a PBI film having a film thickness of 20 μm was obtained. The performance of the PBI coating thus obtained is shown in Table 2. PBI of this embodiment
It should be noted that the coating is more abrasion resistant than that of Example 1.

[0028]

Example 3 The same operation as in Example 1 was performed except that 15% by weight of PTFE powder (Hostaflon (registered trademark) TF9205, manufactured by Hoechst AG) was added to the PBI solution. As a result, a PBI film having a film thickness of 20 μm was obtained. The performance of the PBI coating thus obtained is shown in Table 2.
Shown in. It should be noted that the PBI coating of this example has a particularly low coefficient of friction.

[0029]

Example 4 The same operation as in Example 2 was carried out except that 15% by weight of PTFE powder (Hostaflon TF9205) was added to the PBI solution. As a result, the film thickness 2
A 0 μm PBI coating was obtained. The performance of the PBI coating thus obtained is shown in Table 2. It should be noted that the PBI coating of this example has a particularly low coefficient of friction. In addition, the PBI coating of this embodiment is the PBI coating of the third embodiment.
It should be noted that the wear resistance is higher than that of the coating.

[0030]

Example 5 The same PBI as in Example 1 was used. PBI
Was dissolved in N, N-dimethylacetamide to give a concentration of 2
A 0 wt% PBI solution was prepared. The substrate has a diameter of 30
A mm aluminum roll was used. The room temperature (23 ° C.) PBI solution was applied to the surface of an aluminum roll also at room temperature (23 ° C.) by a roll coater. Then
The coating film was dried from a starting temperature of 60 ° C at a heating rate of 2 ° C / min. The final temperature was 200 ° C. As a result, a PBI coating having a film thickness of 1 mm was obtained on the surface of the aluminum roll. The performance of the resulting PBI coating is shown in Table 2.

[0031]

Example 6 The same PBI as in Example 1 was used. PBI
Was dissolved in N, N-dimethylacetamide to give a concentration of 3
A 0 wt% PBI solution was prepared. The substrate has a diameter of 30
A mm aluminum roll was used. PBI solution 60
After preheating to 0 ° C, the PBI solution was applied to the surface of an aluminum roll at room temperature (23 ° C) by a roll coater. Next, the coating film was dried at a temperature rising rate of 1 ° C./minute from the starting temperature of 60 ° C. The final temperature was 200 ° C.
As a result, a PBI coating having a film thickness of 2 mm was obtained on the surface of the aluminum roll. The performance of the resulting PBI coating is shown in Table 2.

[0032]

Example 7 The same PBI as in Example 1 was used. PBI
Was dissolved in N, N-dimethylacetamide to give a concentration of 5
A wt% PBI solution was prepared. The base has a diameter of 30 m
m aluminum roll was used. PBI solution at 60 ℃
After preheating, the PBI solution was applied to the surface of an aluminum roll at room temperature (23 ° C.) by a roll coater. Next, the coating film was dried at a temperature rising rate of 10 ° C./minute from the starting temperature of 60 ° C. The final temperature was 200 ° C.
As a result, a film thickness of 10 μm was formed on the surface of the aluminum roll.
A PBI coating of The performance of the resulting PBI coating is shown in Table 2.

[0033]

Example 8 The same PBI as in Example 1 was used. PBI
Was dissolved in N, N-dimethylacetamide to give a concentration of 3
A 0 wt% PBI solution was prepared. The substrate has a diameter of 30
A mm aluminum roll was used. After preheating the PBI solution and the aluminum roll to 60 ° C., the PBI solution was applied to the surface of the aluminum roll by a roll coater. Next, the coating film was dried at a temperature rising rate of 1 ° C./minute from the starting temperature of 60 ° C. The final temperature was 200 ° C. As a result, on the surface of the aluminum roll, the film thickness 2
A mm PBI coating was obtained. The performance of the resulting PBI coating is shown in Table 2.

[0034]

Comparative Example 1 The same PBI as in Example 1 was used. PBI
Was dissolved in N, N-dimethylacetamide to give a concentration of 1
A 0 wt% PBI solution was prepared. The substrate has a diameter of 30
A mm aluminum roll was used. PBI solution 60
After preheating to 0 ° C, the PBI solution was applied to the surface of an aluminum roll at room temperature (23 ° C) by a roll coater. Next, the coating film was dried at a temperature rising rate from the starting temperature of 60 ° C to 28 ° C / min. The final temperature was 200 ° C. As a result, a film thickness of 20
A μm PBI coating was obtained.

In the obtained PBI coating, bubbles were generated by heating and evaporation, and residual solvent was observed. Also, this P
The adhesion of the BI coating to the substrate was the PB obtained in Example 1.
It was inferior to the I film. The results are shown in Table 2.

[0036]

Comparative Example 2 The same PBI as in Example 1 was used. PBI
Was dissolved in N, N-dimethylacetamide to give a concentration of 1
A 0 wt% PBI solution was prepared. The substrate has a diameter of 30
A mm aluminum roll was used. PBI solution 60
After preheating to 0 ° C, the PBI solution was applied to the surface of an aluminum roll at room temperature (23 ° C) by a roll coater. Next, the coating film was dried while maintaining the starting temperature of 200 ° C. As a result, a 20 μm-thick PBI coating film was obtained on the surface of the aluminum roll.

In the obtained PBI coating, bubbles were generated by heating and evaporation, and residual solvent was observed. Also, this P
The adhesion of the BI coating to the substrate was the PB obtained in Example 1.
It was inferior to the I film. The results are shown in Table 2.

[0038]

Comparative Example 3 The same PBI as in Example 1 was used. PBI
Was dissolved in N, N-dimethylacetamide to give a concentration of 3
A 0 wt% PBI solution was prepared. The substrate has a diameter of 30
A mm aluminum roll was used. After preheating the PBI solution and the aluminum roll to 60 ° C., the PBI solution was applied to the surface of the aluminum roll by a roll coater. Next, the coating film was dried at a temperature rising rate from the starting temperature of 60 ° C to 28 ° C / min. The final temperature was 200 ° C. As a result, a PBI coating having a film thickness of 2 mm was obtained on the surface of the aluminum roll.

In the obtained PBI coating, bubbles were generated by heating and evaporation, and residual solvent was observed. Also, this P
The adhesion of the BI coating to the substrate was the PB obtained in Example 1.
It was inferior to the I film. The results are shown in Table 2.

[0040]

Comparative Example 4 The same PBI as in Example 1 was used. PBI
Was dissolved in N, N-dimethylacetamide to give a concentration of 3
A 0 wt% PBI solution was prepared. The substrate has a diameter of 30
A mm aluminum roll was used. After preheating the PBI solution and the aluminum roll to 60 ° C., the PBI solution was applied to the surface of the aluminum roll by a roll coater. Next, the coating film was dried while maintaining the starting temperature of 200 ° C. As a result, a PBI coating having a film thickness of 2 mm was obtained on the surface of the aluminum roll.

In the obtained PBI coating, bubbles were generated by heating and evaporation, and residual solvent was observed. Also, this P
The adhesion of the BI coating to the substrate was the PB obtained in Example 1.
It was inferior to the I film. The results are shown in Table 2.

[0042]

[0043]

As described above, according to the present invention, the PBI
High strength, high heat resistance, high heat insulation property, chemical resistance, abrasion resistance and low friction property are easily realized on the substrate by forming a coating film, and a new material with a modified surface is provided. You can
Such a material is useful in various fields including a toner fixing device of an electrophotographic copying machine which is particularly required to have high heat resistance and abrasion resistance.

Claims (8)

[Claims] 1. A method for forming a film of polybenzimidazole (PBI), which comprises: (1) forming a film of a PBI solution on a substrate; and (2) setting the temperature of the film to 50 to 50 ° C. 70 to 150-2
Drying the coating film by gradually increasing the temperature to 20 ° C .; 2. The dried PBI coating film has a thickness of 300 to 50.
The method according to claim 1, further comprising the step of heating to 0 ° C. 3. The method according to claim 1, wherein the PBI solution contains an internally added filler. 4. The method according to claim 1, wherein the PBI solution contains a binder resin substance. 5. The solvent of the PBI solution is at least one selected from the group consisting of N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide and N-methyl-2-pyrrolidone. ~
4. The method according to any one of 4 above. 6. The method of claim 5, wherein the solvent further comprises terpenes and / or ketones. 7. The substrate and / or the PBI solution comprises:
The method according to any one of claims 1 to 6, which has been preheated to 50 to 100 ° C. 8. The method according to claim 1, wherein the temperature rise in the step (2) is 15 ° C./min or less.